Plug and Play upgrade harnesses?

Anyone ever use these to help with the high wattage bulbs. I know your suppsed to use a relay too. I just am not sure how this whole setup works and what to do. Any info and not just about high wattage bulbs suck, get silverstars blah blah blah. Real help please. How do these plug and play ones work and the originals? Is the relay needed? How does it all get wired? Thanks